1. Field of the Invention
This invention relates to a method of making a fine powder of a metallic compound having ceramic coatings thereon. The fine powder of a metallic compound obtained by the method of the invention is suitably used as a sintering material.
2. Description of the Prior Art
As is well known in the art, sintering of a metallic compound powder such as silicon nitride powder does not smoothly proceed when using the metallic compound powder alone. It is the usual practice to add, to metallic compound powder, sintering aids such as yttrium oxide, aluminium oxide and the like.
In order to cause the sintering to proceed smoothly, it is preferred that a metallic compound powder and a sintering aid are uniformly mixed to make a larger contact area thereof.
However, since the metallic compound powder and the sintering aid are both in the form of powders, it is difficult to mix the powders substantially uniformly, with an attendant problem that the strength of the sintered product may not be satisfactory depending on the degree of uniformity in the mixing.
Further, the metallic compound powder is too large to obtain the strong sintered product.